High speed data communication networks often use optical transceivers to transmit and receive optical signals carrying digitally encoded data. Optical transceivers typically use an optical transmitter, such as a laser, to transmit optical signals and an optical receiver, such as a photodiode, to receive optical signals. Conventional transceivers require a pair of optical fibers to implement full-duplex functionality. One optical fiber connects with the optical transmitter while the other optical fiber connects with the optical receiver.
Advancements in optical data communication technology have enabled bidirectional data transmission over a single optical fiber. These bidirectional communication systems can allow for data to be transmitted in both directions over a single optical fiber instead of requiring an individual optical fiber for each direction of data transmission. Bidirectional communication technology increases bandwidth by essentially doubling the data payload capacity. While bidirectional communication in optical networks can increase the amount of information that can be transmitted and received, these networks may still be affected by data transmission errors. Such errors can be caused, for example, by improper laser driver power control or modulation.
Diagnostic information is often used to address these types of problems. However, conventional diagnostic functions are open-loop in nature. For example, an optical transmitter can report its own output power and an optical receiver can report its own received optical power. While the optical transmitter or the optical receiver can provide useful diagnostic information, the diagnostic information may not be at the location best suited to utilize the information and implement a correction procedure because of the open-loop nature of the system. For example, an optical receiver that reports low optical power cannot be used by the optical transmitter that transmitted the optical signal. In other words, human intervention is typically needed to fix any problems indicated by the diagnostic information provided by the optical transmitter or the optical receiver. Further, conventional optical transceivers cannot self-compensate to maintain the integrity of the optical data when the data link degrades.
Yet another problematic aspect of optical communication networks relates to the validation or integrity of an optical link that is desirably established between a pair of optical transceiver modules. Unlike its electrical analog, i.e., copper cabling including CAT-5 and LAN connections, wherein a user can visually or otherwise verify the establishment of a link between two ends of the connection, no indicator is available to verify when a reliable optical link between two transceivers has been established.
Thus, when a problem condition exists, such as a faulty transmitting or receiving port, a contaminated optical fiber end face, a broken or kinked optical fiber, an incompatible transceiver pairing at either end of the link, etc., it may prove difficult for a technician to debug the condition, given the relative difficulty in determining at the outset whether a valid link is even established between the transceivers. In such a case, the technician or user must instead rely on the host system on either end of the problem link for information regarding whether a data link has been acceptably established. This in turn makes the technician or user relatively more reliant on the host system(s) and their particular on-board software, which further complicates the debugging process.
It is noted that a receiving port of an optical transceiver module linked to another transceiver can employ loss of signal (“LOS”) or signal detect (“SD”) functions as part of an industry standard in order to indicate the absence (LOS) or presence (SD) of an optical signal at the receiving port. Unfortunately, however, no analogous indicators are available on the transmitting port of the linked transceiver. This is because receiving ports have been traditionally incapable of transmitting information regarding the presence of a link therebetween.
It is therefore seen that a need exists for an indicator or other identifier to be available on the transmitting end of a data link between an optical transmitter and optical receiver, such as in the case of two linked optical transceiver modules. Specifically, a need exists for an optical receiver that is capable of communicating data regarding the successful establishment of an optical data link between it and a remotely situated optical transmitter. Any solution to these needs should further facilitate a technician or other user to readily debug the link without excessive reliance on the host systems in which the optical transmitter and optical receiver reside.